My symmetry is off but only on the lower jaw of my model?
At a glance, it looks like the lower jaw is a separate object (correct?) and that the origin of that object has been accidentally moved somehow. In Object Mode, select the jaw, right click, and go to "Set Origin". You should see a few options; select "Origin to Center of Mass (Surface)". That should get your origin back to the right place and fix the symmetry.